Magnetoresistive effect elements such as a giant magnetoresistive effect (GMR) element and a tunnel magnetoresistive effect (TMR) element having a configuration in which a reference layer as a magnetization fixed layer, a non-magnetic spacer layer, and a magnetization free layer are stacked in this order are known. Among the magnetoresistive effect elements, the TMR element that uses an insulation layer (tunnel barrier layer) as the non-magnetic spacer layer generally has high element resistance but can realize a high magnetoresistive (MR) ratio, compared to the GMR element that uses a conductive layer as the non-magnetic spacer layer. Thus, the TMR element has drawn attention as an element used in a magnetic sensor, a magnetic head, a magnetoresistive random access memory (MRAM), and the like (for example, Patent Literatures 1 and 2 below).
A technology called “spin injection magnetization reversal” in which a spin transfer torque (STT) is applied to the magnetization free layer from electron spins by causing a spin-polarized current to flow through the magnetization free layer is known as a method of reversing the magnetization direction of the magnetization free layer of the TMR element. For example, applying this technology to the MRAM can reduce the size of a memory cell and thus can achieve high density for the reason that an interconnect for magnetic field generation for reversing the magnetization direction of the magnetization free layer is not necessary. Generally, the MRAM that uses the magnetization reversal technology based on the STT is called an “STT-MRAM”.
The use of the TMR element that has perpendicular magnetic anisotropy is considered in order to further achieve high density in the MRAM or the like (for example, Patent Literatures 3 to 5 below). In such a TMR element, the magnetization direction of the reference layer is fixed in a perpendicular direction (the stack direction of the element; that is, a direction orthogonal to the in-plane direction of each layer), and the easy magnetization axis of the magnetization free layer is also in the perpendicular direction. Accordingly, since the amount of current needed for spin injection magnetization reversal can be reduced, the size of a selection transistor for selecting the TMR element can be reduced. Consequently, in the case of using the TMR element having perpendicular magnetic anisotropy, high density can be achieved since the size of the memory cell can be reduced compared to that in the case of using the TMR element that has in-plane magnetic anisotropy.